Efforts to assess the efficiency and performance of our new MALDI-ITMS were initiated in our lab recently. A trapping strategy termed matched trapping, which utilizes most of the ion population of the wide kinetic energy distribution by properly timing the RF trapping field to match the energy distribution of the desorbed ions, achieved a trapping efficiency >30% as measured directly; advances in the understanding of resonant ejection lead to improved detection parameters for mass range extension which improved detection efficiency by more than a order of magnitude; a careful investigation of mass isolation revealed that if no discontinuity of the RF field is present in the scan functions, a mass isolation efficiency of better than 90% could be achieved. These features make sensitive MS/MS practical with ITMS. The success of this undertaking, paved the way for the development of a practical sensitive biological ITMS (see highlights #6 and #7) . We have published a series of three papers describing the instrument and its performance in Anal. Chem. 1996. Subsequently, we used the new instrument to solve a series of challenging biological problems (a selection of which is reported in (Qin et al, Anal. Chem. 69, (1997) 3995-4001, and Qin and Chait, 69, (1997) 4002-4005.